In aircraft applications, motion is known to be transmitted from an input shaft to an output shaft using a face gear transmission assembly, which comprises two coaxial, counter-rotating face gears positioned facing each other, and a transmission pinion meshing with both face gears.
To reduce action at the face gear-transmission pinion mesh points, a number of transmission pinions are used, each of which is normally supported by a respective elastically deformable member permitting movement of the transmission pinion in a circumferential direction of the face gears. That is, each deformable member extends perpendicular to the face gear axes, and is flexible in the plane perpendicular to the face gear axes so as to permit, in use, independent relative movements of the transmission pinions in said perpendicular plane.
Though widely used, by adapting to different operating conditions, known transmissions of the type described above are unsatisfactory in terms of size and weight. This is mainly due to the fact that, in known solutions, the actions or forces exchanged at the various face gear-transmission pinion mesh points and under different operating conditions normally differ in value, are difficult to assess, and are directed in respective directions forming varying angles, which are also unpredictable by depending on the yield or flexural strength of, and the loads transmitted to, the various deformable supporting members used.
As a result, the various actions exchanged are transmitted at least partly and unpredictably onto the face gear supports, and the various parts of the transmission, face gears included, must be sized on the basis of an assumed maximum potential value of such actions, so that, in most applications, the transmission is oversized and therefore excessively heavy, bulky and, above all, expensive.